Final answer:
Most cases heard by the Supreme Court reach it under a writ of certiorari, where at least four justices must agree to grant the writ for the case to be heard. Original jurisdiction of the Supreme Court is rare and only applies to specific types of cases.
Step-by-step explanation:
The majority of cases that the Supreme Court hears reach it under writ of certiorari. This legal process involves the Supreme Court calling up the records of the lower court so the case can be reviewed. The court has the discretion to grant a writ of certiorari and only does so when cases present a constitutional question or when there is conflicting interpretation of a law among lower courts. The Rule of Four requires that at least four out of the nine justices must agree to accept a case under the writ of certiorari.
Despite having both original and appellate jurisdiction, the vast majority of cases under the Supreme Court's review are appellate cases. Original jurisdiction is exercised in rare circumstances, such as disputes between states or cases involving foreign ambassadors, whereas appellate jurisdiction allows the Supreme Court to hear cases on appeal from lower courts, which constitutes the bulk of its docket.